Field of the Invention
The present invention relates to color filter arrays for image sensors.
Description of the Related Art
In electronic color imaging, it is desirable to simultaneously capture image data in three color planes, usually red, green and blue. When the three color planes are combined, it is possible to create high-quality color images. Capturing these three sets of image data can be done in a number of ways. In electronic photography, this is sometimes accomplished by using a single two dimensional array of sensors that are covered by a pattern of red, green and blue filters. This type of sensor is known as a color filter array or CFA. FIG. 1 is a diagram of a conventional Bayer pattern. FIG. 1 shows that the red (R), green (G) and blue (B) pixels as are commonly arranged in a Bayer pattern on a CFA sensor.
When a color image is captured using a CFA, it is necessary to interpolate the red, green and blue values so that there is an estimate of all three color values for each sensor location. Once the interpolation is done, each picture element, or pixel, has three color values and can be processed by a variety of known image processing techniques depending on the needs of the system. Some examples of the reasons for processing are to do image sharpening, color correction or half toning.
The diagram below shows how red green and blue pixels can be arranged in a particular color filter array pattern, hereinafter referred to as the “Bayer pattern”. Because the red, green, and blue filters absorb two thirds of the incident light, such CFA sensors tend to be photometrically slow.
Additionally, the blue cones have a lower density at the center of the fovea of the human eye, and thus the maximum acuity for blue light is lower than that of other colors. Accordingly, there is a demand for a color filter array having a lower density of the color blue, thereby increasing the overall acuity of the primary color components in the image captured by the image sensor.